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71.
Mohsan Nawaz Faiza Jan Iftikhar Musa Kaleem Baloch Wajid Rehman Iftikhar Ahmad 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(13):2169-2172
Single-phase giant magnetoresistance (GMR) compounds were prepared by doping the parent compound, NdMnO3, with Sr at Nd sites. The resistivity of the doped samples showed two prominent regions (Δρ/ΔT < 0, insulating and Δρ/ΔT > 0, metallic). The doped samples exhibited an enhancement in double exchange (DE) interactions causing an increase in T
c (transition temperature). Magnetic field decreased the resistance of all the samples because of the suppression of spin fluctuations
and an increase in disorder in the system. The polaron and variable range hopping (VRH) models were good for studying the
transport mechanism of electrons and understand their behavior at T > T
c. 相似文献
72.
Maryam Ataeefard Siamak Moradian Mojtaba Mirabedini Morteza Ebrahimi Saeed Asiaban 《Plasma Chemistry and Plasma Processing》2008,28(3):377-390
The surface of a LDPE was modified by Ar, O2, N2, CO2 gaseous plasma. The changes in surface morphology and surface wettability were investigated using AFM and SEM. The surface
chemical changes of LDPE were also characterized by FTIR-ATR. The SEM and AFM results demonstrated variable changes in surface
roughness for different types of plasma gas used, the changes being more for the Ar and N2 plasma treatments. Considering the nature of the LDPE film, XRD studies were carried out to determine changes in the percentage
crystalinity. The results showed that all low pressure O2, Ar, N2, CO2 gas plasmas improved the wettability of LDPE films. Contact angles decreased significantly depending on the discharge powers
and exposure times. Surface morphology was also found to vary with plasma discharge powers, exposure times, and the type of
gas being used. Ar and N2 gas plasmas in general produced more superior results. 相似文献
73.
Mohammad Ali Zolfigol Kamal Amani Maryam Hajjami Arash Ghorbani-Choghamarani 《Monatshefte für Chemie / Chemical Monthly》2008,121(4):895-899
A wide range of aliphatic or aromatic sulfides are selectively oxidized to the corresponding sulfoxides using ammonium cerium
(IV) nitrate (CAN) and a catalytic amount of KBr or NaBr in the presence of wet SiO2 in CH2Cl2 under heterogeneous conditions in moderate to high yields. 相似文献
74.
Isoquinoline reacts with ethyl bromopyruvate in the presence of dialkyl acetylenedicarboxylates or diaryloylacetylenes to produce dialkyl 1-(2-ethoxy-2-oxoacetyl)pyrrolo[2,1-a]isoquinoline-2,3-dicarboxylates or ethyl 2-[2,3-diaryloylpyrrolo[2,1-a]isoquinoline-1-yl]-2-oxoacetates in good yields. 相似文献
75.
Choudhary MI Siddiqui ZA Musharraf SG Nawaz SA Atta-Ur-Rahman 《Natural product research》2005,19(4):311-317
The microbial transformation of prednisone (17alpha,21-dihydroxy-pregna-1,4-diene-3,11,20-trione) (1) by Cunninghamella elegans afforded two metabolites, 17alpha,21-dihydroxy-5alpha-pregn-1-ene-3,11,20-trione (2) and 17alpha,20S,21-trihydroxy-5alpha-pregn-1-ene-3,11-dione (3), while the fermentation of 1 with Fusarium lini, Rhizopus stolonifer and Curvularia lunata afforded a metabolite 1,4-pregnadiene-17alpha,20S,21-triol-3,11-dione (4). Compound 3 was found to be a new metabolite. Their structures were elucidated on the basis of spectroscopic techniques. Compound 3 showed inhibitory activity against lipoxygenase enzyme. 相似文献
76.
Copper/Graphene/Clay Nanohybrid: A Highly Efficient Heterogeneous Nanocatalyst for the Synthesis of Novel 1,2,3‐Triazolyl Carboacyclic Nucleosides via ‘Click’ Huisgen 1,3‐Dipolar Cycloaddition 下载免费PDF全文
Mohammad Navid Soltani Rad Somayeh Behrouz S. Jafar Hoseini Hasan Nasrabadi Maryam Saberi Zare 《Helvetica chimica acta》2015,98(9):1210-1224
A very mild and highly efficient synthesis of some novel 1H‐1,2,3‐triazolyl carboacyclic nucleosides via a ‘Click’ Huisgen cycloaddition of N‐propargyl nucleobases and azido alcohols using Cu/aminoclay/reduced graphene oxide nanohybrid (Cu/AC/r‐GO nanohybrid) as nanocatalyst is described. The preparation and characterization of Cu/AC/r‐GO nanohybrid are discussed. This catalyst was characterized by X‐ray diffraction, FT‐IR, TEM, and energy‐dispersive analysis of X‐ray techniques. Cu/AC/r‐GO nanohybrid is a stable and highly efficient heterogeneous nanocatalyst that can be easily prepared, used, and restored from the reaction mixture by simple filtration, and reused for many consecutive trials without significant decrease in activity. 相似文献
77.
A microextraction procedure based on a task‐specific ionic liquid for the separation and preconcentration of lead ions from red lipstick and pine leaves 下载免费PDF全文
Asma Saljooqi Tayebeh Shamspur Maryam Mohamadi Daryoush Afzali Ali Mostafavi 《Journal of separation science》2015,38(10):1777-1783
First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task‐specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho‐positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0–24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination. 相似文献
78.
Ester Sagristà Estelle Larsson Maryam Ezoddin Manuela Hidalgo Victòria Salvadó Jan Åke Jönsson 《Journal of chromatography. A》2010,1217(40):6153-6158
In this study, a three-phase hollow fiber liquid-phase microextraction (HF-LPME) method combined with liquid chromatography–mass spectrometry was developed for direct determination of four non-steroidal anti-inflammatory drugs (ketoprofen, naproxen, diclofenac and ibuprofen) in sewage sludge. The drugs were extracted from non-spiked and spiked slurry samples with different amounts of sludge into an organic phase and then back-extracted into an aqueous phase held in the lumen of the hollow fiber. High enrichment factors ranging from 2761 to 3254 in pure water were achieved. In sludge samples, repeatability and inter-day precision were tested with relative standard deviation values between 10–18% and 7–15%, respectively. Average concentrations of 29 ± 9, 138 ± 2, 39 ± 5 and 122 ± 7 ng/g were determined in dried sludge from Källby sewage treatment plant (Sweden) for ketoprofen, naproxen, diclofenac and ibuprofen, respectively. 相似文献
79.
Jahan Bakhsh Raoof Reza Ojani Maryam Ramine 《Journal of Solid State Electrochemistry》2009,13(9):1311-1319
A p-duroquinone (tetramethyl-p-benzoquinone) modified carbon paste electrode (DMCPE) was employed to study the electrocatalytic reduction of nitrite in
aqueous solutions using cyclic voltammetry (CV), double potential-step chronoamperometry, and differential pulse voltammetry
(DPV). It has found that under an optimum condition (pH 1.00), the reduction of nitrite at the surface of DMCPE occurs at
a potential of about 660 mV less negative than that of an unmodified carbon paste electrode (CPE). The catalytic rate constant,
k′h, based on Andrieux and Saveant theoretical model was calculated as for scan rate 10 mV s-1. Also, the apparent diffusion coefficient, D
app, was found as 2.5 × 10–10 and 3.61 × 10–5 cm2 s-1
for p-duroquinone in carbon paste matrix and nitrite in aqueous buffered solution, respectively. The values for αnα were estimated to be −0.65 and −0.19 for the reduction of nitrite at the surface of DMCPE and CPE, respectively. The electrocatalytic
reduction peak currents showed a linear dependence on the nitrite concentration, and a linear analytical curve was obtained
in the ranges of 5.0 × 10–5 M to 8.0 × 10–3 M and 6.0 × 10–6 M to 8.0 × 10–4 M of nitrite concentration with CV and DPV methods, respectively. The detection limits (2σ) were determined as 2.5 × 10–5 M and 4.3 × 10–6 M by CV and DPV methods. This method was also applied as a simple, selective and precise method for determination of nitrite
in real samples (the weak liquor from the wood and paper factory of Mazandaran province in Iran) by using a standard addition
method. 相似文献
80.
On irradiation in the presence of propen‐2‐yl isocyanate ( 4 ), six‐membered cyclic enones 3 are converted into regio‐ and stereoisomeric mixtures of [2+2] cycloadducts 5 – 10 ; the preferentially formed HT products, 5 – 8 , can be converted into the corresponding bicyclic amines by acid hydrolysis, whereas, under these conditions, the regioisomeric HH‐isocyanato derivatives undergo a retro‐Mannich reaction. 相似文献